This project evaluates the potential of erbB-2/neu gene immunotherapy for neoplastic disease. ErbB-2 is a proto-oncogene that encodes a group I tyrosine kinase similar to that of the epidermal growth factor receptor. Although its expression ordinarily is negligible in most normal adult tissues, it is amplified and/or over-expressed in 20-30% of all invasive breast tumors and in several other types of adenocarcinomas. High-level expression of erbB-2 likely plays a role in tumor etiopathogenesis, as transgenic mice that aberrantly express neu (the rodent homologue to erbB- 2) spontaneously develop mammary tumors that express high-levels of this proto-oncogene. Accordingly, erbB-2/neu encodes an attractive target antigen for immunotherapy. We developed neu plasmid DNA expression vectors (designated as "neu DNA vaccines") for direct in vivo somatic cell transfection to induce immune responses to the protein product of neu, namely pl85neu. Preliminary data suggest that injection into muscle of such neu DNA vaccines can induce protective immunity against adoptive transfer of syngeneic neu-expressing mammary tumor cells, as well as prevent or delay the onset of de novo mammary tumors in neu-transgenic mice. This proposal seeks to develop further this new vaccine technology with the following specific aims: (1) compare the effectiveness of intradermal versus intramuscular injection of neu DNA vaccines in inducing protective immunity against adoptive transfer of a syngeneic neu- expressing mouse mammary tumor cell line, designated Tgl-l, in neu- transgenic mice; (2) examine whether in vivo somatic cell co-transfection of naked DNA plasmid vectors that direct synthesis of Th1 versus Th2- associated cytokines can pattern the type of helper T cell response to pl85neu induced by neu DNA vaccines and enhance or deter the protective immunity afforded by neu DNA immunization; (3) examine whether I)I Vivo somatic cell co-transfection of plasmid DNA that directs synthesis of murine CD80 can enhance the protective immunity induced by neu DNA vaccines; (4) evaluate whether neu expression constructs that direct synthesis of intracellular pl85neu with higher rates of poly-ubiquination and intracellular proteolysis have improved efficacy in stimulating cellular immunity against tumor cells that express this proto-oncogene; (5) map the epitope(s) of pl85neu that can induce anti-pl85neu antibodies that influence the receptor signaling or the growth of neu-expressing mouse mammary tumor cells; (6) compare methods of neu DNA immunization for their ability to prevent, delay, or accelerate the de novo development of mammary tumors in neu-transgenic mice; and (7) evaluate for local or systemic pathology induced by neu DNA vaccines in neu-transgenic mice. Through these studies we may develop improved strategies for immunotherapy of neoplasms that express high levels of the erbB-2 proto-oncogene.